|Authors||M. J. Sætra, A. J. Ellingsrud and M. E. Rognes|
|Title||Modeling electrodiffusive, osmotic, and hydrostatic interplay in astrocyte networks|
|Project(s)||Department of Numerical Analysis and Scientific Computing, Waterscales: Mathematical and computational foundations for modeling cerebral fluid flow|
|Year of Publication||2022|
|Publisher||Society for Neuroscience|
|Place Published||Neuroscience 2022|
During high neuronal activity, the intra- and extracellular ion concentrations change. These changes affect the osmotic pressure gradients across the membranes of both neurons and astrocytes, leading to water movement and cellular swelling. We asked: Can swelling generate a hydrostatic pressure gradient of sufficient magnitude to drive non-negligible fluid flow within astrocytes or the extracellular space ? As it is currently infeasible to measure such intracellular pressure gradients in vivo, computational modeling emerges as a viable alternative to study the interplay between osmotic and hydrostatic forces at the microscale.
In this study, we present a computational model of ionic electrodiffusion, hydrostatic pressures, and transmembrane- and intracompartmental fluid flow in a homogenized astrocytic syncytium surrounded by extracellular space. The model builds on previous models of ionic electrodiffusion [2,3], and potassium buffering . Our findings show that increases in extracellular potassium concentrations in response to neuronal activity induce swelling and hydrostatic pressure gradients within the intra- and extracellular spaces. The fluid flow induced by these hydrostatic pressure gradients alone did not have a significant effect on the transport of potassium within any of the compartments. However, when also accounting for fluid flow induced by osmotic gradients within the astrocytic syncytium, convection played a considerable role in potassium clearance. These findings point at a mechanistic understanding of how astrocytic permeability may impact fluid flow in the brain.
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